Added minivec type

src/minivec.h

@@ -0,0 +1,156 @@
+#ifndef MINIVEC_H
+#define MINIVEC_H
+
+#include <float.h>
+
+#define MINIVEC_MAX_DIM 16000
+
+#define fp8 uint8
+
+#define MINIVEC_SIZE(_dim)		(offsetof(MiniVector, x) + sizeof(fp8)*(_dim))
+#define DatumGetMiniVector(x)		((MiniVector *) PG_DETOAST_DATUM(x))
+#define PG_GETARG_MINIVEC_P(x)	DatumGetMiniVector(PG_GETARG_DATUM(x))
+#define PG_RETURN_MINIVEC_P(x)	PG_RETURN_POINTER(x)
+
+typedef struct MiniVector
+{
+	int32		vl_len_;		/* varlena header (do not touch directly!) */
+	int16		dim;			/* number of dimensions */
+	int16		unused;			/* reserved for future use, always zero */
+	fp8			x[FLEXIBLE_ARRAY_MEMBER];
+}			MiniVector;
+
+MiniVector *InitMiniVector(int dim);
+
+/*
+ * Check if fp8 is NaN
+ */
+static inline bool
+Fp8IsNan(fp8 num)
+{
+	return (num & 0x7F) == 0x7F;
+}
+
+/*
+ * Check if fp8 is zero
+ */
+static inline bool
+Fp8IsZero(fp8 num)
+{
+	return num == 0;
+}
+
+/*
+ * Convert a fp8 to a float4
+ */
+static inline float
+Fp8ToFloat4(fp8 num)
+{
+	float		lookup[128] = {0, 0.00195312, 0.00390625, 0.00585938, 0.0078125, 0.00976562, 0.0117188, 0.0136719, 0.015625, 0.0175781, 0.0195312, 0.0214844, 0.0234375, 0.0253906, 0.0273438, 0.0292969, 0.03125, 0.0351562, 0.0390625, 0.0429688, 0.046875, 0.0507812, 0.0546875, 0.0585938, 0.0625, 0.0703125, 0.078125, 0.0859375, 0.09375, 0.101562, 0.109375, 0.117188, 0.125, 0.140625, 0.15625, 0.171875, 0.1875, 0.203125, 0.21875, 0.234375, 0.25, 0.28125, 0.3125, 0.34375, 0.375, 0.40625, 0.4375, 0.46875, 0.5, 0.5625, 0.625, 0.6875, 0.75, 0.8125, 0.875, 0.9375, 1, 1.125, 1.25, 1.375, 1.5, 1.625, 1.75, 1.875, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 28, 30, 32, 36, 40, 44, 48, 52, 56, 60, 64, 72, 80, 88, 96, 104, 112, 120, 128, 144, 160, 176, 192, 208, 224, 240, 256, 288, 320, 352, 384, 416, 448, NAN};
+	float		v = lookup[num & 0x7F];
+
+	return (num & 0x80) == 0x80 ? -v : v;
+}
+
+/*
+ * Convert a float4 to a fp8
+ */
+static inline fp8
+Float4ToFp8Unchecked(float num)
+{
+	union
+	{
+		float		f;
+		uint32		i;
+	}			swapfloat;
+
+	uint32		bin;
+	int			exponent;
+	int			mantissa;
+	uint8		result;
+
+	swapfloat.f = num;
+	bin = swapfloat.i;
+	exponent = (bin & 0x7F800000) >> 23;
+	mantissa = bin & 0x007FFFFF;
+
+	/* Sign */
+	result = (bin & 0x80000000) >> 24;
+
+	if (isinf(num) || isnan(num))
+	{
+		/* NaN */
+		result |= 0x7F;
+	}
+	else if (exponent > 116)
+	{
+		int			m;
+		int			gr;
+		int			s;
+
+		exponent -= 127;
+		s = mantissa & 0x000FFFFF;
+
+		/* Subnormal */
+		if (exponent < -6)
+		{
+			int			diff = -exponent - 6;
+
+			mantissa >>= diff;
+			mantissa += 1 << (23 - diff);
+			s |= mantissa & 0x000FFFFF;
+		}
+
+		m = mantissa >> 20;
+
+		/* Round */
+		gr = (mantissa >> 19) % 4;
+		if (gr == 3 || (gr == 1 && s != 0))
+			m += 1;
+
+		if (m == 8)
+		{
+			m = 0;
+			exponent += 1;
+		}
+
+		if (exponent > 8)
+		{
+			/* Infinite, which is NaN */
+			result |= 0x7F;
+		}
+		else
+		{
+			if (exponent >= -7)
+				result |= (exponent + 7) << 3;
+
+			result |= m;
+		}
+	}
+
+	return result;
+}
+
+/*
+ * Convert a float4 to a fp8
+ */
+static inline fp8
+Float4ToFp8(float num)
+{
+	fp8			result = Float4ToFp8Unchecked(num);
+
+	if (unlikely(Fp8IsNan(result)) && !isnan(num))
+	{
+		char	   *buf = palloc(FLOAT_SHORTEST_DECIMAL_LEN);
+
+		float_to_shortest_decimal_buf(num, buf);
+
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("\"%s\" is out of range for type minivec", buf)));
+	}
+
+	return result;
+}
+
+#endif